Reflex to direct photocopying method and apparatus

ABSTRACT

A method and device for producing electrophotographic copies of opaque documents or documents printed on both sides, through reflex exposure of commercial electrophotographic papers, films, or the like. The original document is placed face-to-face with the electrophotographic surface which has been especially preconditioned for reflex exposure by electrostatic charge limitation. The electrophotographic surface is exposed to a specially limited quantity of light directed through it to the face of the original document, the assembled pair being maintained in close contact during the exposure. Following exposure, an image is developed on the electrophotographic surface by electrostatic toning. The developed reflex image is a reversal of the original so that right-reading copies of the original are made from it by face-to-face reproduction means, such as by a direct exposure electrophotographic contact printing operation.

United States Patent [72] Inventor F. Sutherland Macltlem 3,335,003 8/ 1967 Snelling 355/ l 2 X New Canaan, Conn. 1 PP No. 779,057 Pnrnary Examiner-Samuel S. Matthews Assistant Examiner-Michael Hams [22] Filed 1968 Attorney-Hopgood and Calimafde [45] Patented Oct. 12, 1971 v [73] Assignee Equipment Development Corp.

New Canaan, Conn.

[54] REFLEX TO DIRECT PHOTOCOPYING METHOD ABSTRACT: A method and device for producing electrophotographic copies of opaque documents or documents printed on both sides, through reflex exposure of commercial electrophotographic papers, films, or the like. The original document is placed face-to-face with the electrophotographic surface which has been especially preconditioned for reflex exposure by electrostatic charge limitation. The electrophotographic surface is exposed to a specially limited quantity of light directed through it to the face of the original document, the assembled pair being maintained in close contact during the exposure. Following exposure, an image is developed on the electrophotographic surface by electrostatic toning. The developed reflex image is a reversal of the original so that right-reading copies of the original are made from it by faceto-face reproduction means, such as by a direct exposure elec-' trophotographic contact printing operation.

REFLEX TO DIRECT PI'IOTOCOPYING METHOD AND APPARATUS BACKGROUND The invention is of a small relatively simple and inexpensive ofiice copying machine, based upon the principles of electrophotography and which utilizes commercial electrophotographic copy paper such as zinc oxide Simfax made by S. D. Warren Company or other papers made for the nontransfer electrophotographic process. 7

The invention is unique in that it can make electrophotographic reflex copies of opaque documents, or of documents printed on both sides, and direct copies of translucent or nonopaque documents printed on one side only.

Reflex copying has been attempted by xerographic and other transfer processes, and other methods of making electrophotographic reflex copies have been suggested; however these processes and the equipment and materials utilized were complex and have not proved to be commercially acceptable.

Prior to my invention it was not possible to consistently make electrophotographic reflex copies of documents using any known combination of device and specially manufactured paper. I have discovered how to control the reflex process, so that by following the teaching of my invention one skilled in the art can build a machine which will make consistently good reflex copies using electrophotographic copy paper commercially available.

An object of my invention is to provide a method and device for electrophotographically producing a mirror image copy of a document upon electrophotographic copy paper by reflex exposure, and for producing a plurality of duplicate copies of the document by one-step exposure from this mirror image copy.

Another object of my invention is to provide a nontransfer method and device for making duplicate copies of opaque documents or documents printed on both sides using commercially available zinc oxide electrophotographic paper.

A further objective of my invention is to provide in a single machine the ability to make reflex and direct electrophotographic copies of documents by a nontransfer process.

SUMMARY Briefly, my invention is a nontransfer method and device for electrophotographically copying documents by reflex and direct exposure. A reflex copy is made by placing the original document face-to-face with a sheet of dark-adapted electrophotographic copy paper, charged at a preselected rate, and over a preselected time interval, and then exposing the back of the copy paper so assembled to controlled illumination. The light passes through the copy paper and is absorbed or reflected by the face of the original to the adjacent activated face of the copy paper, producing its laterally reversed image electrostatically thereon. The exposed paper is then developed producing a mirror image of the original. Duplicate electrophotographic copies of the original are made from this reflex copy bydirect exposure with the reflex copy and copy paper placed'face-to-face or back-to-back.

My invention includes a device for making reflex and reflexdirect electrophotographic copies according to the foregoing methods; and direct copies by known methods. It includes an electrostatic charging means to charge the copy paper, exposure means capable of providing at least two distinct levels of illumination, feed rollers which move the original and copy paper through the charger and exposure means at a selected rate, and means to develop an exposed sheet of copy paper. A guide chute and paper holder, used to make reflex and reflexdirect copies, holds the original or a reflex copy thereof on a position from which it is pushed into feed rollers by a sheet of copy paper as the copy paper emerges from the charger. After exposure the original and copy paper are mechanically separated, and the cop processed through a fluid toner to bring out the latent image thereon.

My invention has the following advantages.

Reflex electrophotographic copies can be made of documents using commercially available electrophotographic copy paper, such as zinc oxide paper.

One reflex (mirror image) copy of an original can be used to produce any number of duplicate copies thereof by one-step direct copying.

Both reflex and direct electrophotographic copies can be made on the same machine. 1

My machine is simple in construction, small, light in weight, relatively inexpensive to build; and by using a liquid developer avoids the dust problems associated with transfer copies.

Other objectives, advantages, and various further features of novelty and invention will be pointed out or will occur to those skilled in the art from a reading of the following specification in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a simplified sectional view of my invention illustrating steps in my methodand the important parts of my apparatus;

FIGS. 2, 3 and 4 are fragmentary views of the device of FIG. 1 illustrating the paths taken by an original and its associated sheet of copy paper therethrough during reflex and direct exposure;

FIGS. 5 and 6 illustrate the paths taken by an original and its associated sheet of copy paper through the device of FIG. 1 during direct exposure; and

FIG. 7 illustrates the relative position of the original and its associated sheet of copy paper required for passage through my machine.

DETAILED DESCRIPTION OF MY INVENTION The method of my invention will now be discussed and the steps thereof described as performed within the device illustrated in FIGS. 1 to 7.

A reflex" copy of any original document, as the term is herein employed, is made by bringing it into face-to-face contact with a prepared sheet of electrophotographic paper, and the pair is exposed to light radiating through the electrophotographic copy paper to the face of the original. A fdirect" is made by exposing the original and copy paper, placed in direct contact in any desired relationship, to light radiating through the original to the copy paper.

The sheet of electrophotographic paper to be used in making a reflex copy must be dark adapted for many hours prior to exposure, and must be protected from any substantial preexposure while being placed in the copying device.

The dark-adapted copy paper must be also charged prior to being brought into contact with the original. This may be accomplished by feeding the copy paper through a corona charging unit. For this purpose, a potential 12,000 volts; i.e., plus 6,000 and minus 6,000, between the wires of the charging unit is most advantageous. The charge placed upon the photoconductive surface of the cop paper may be positive or negative depending upon the requirements of the paper.

I have found that the rate or speed at which the copy paper is advanced through the charger, or in other words, the time the copy paper is actually exposed to a given corona unit and thus charged has great bearing on the reflexing qualities of the paper. If the charging rate is relatively slow as in conventional electrostatic copiersunder one-half inch per second-the paper will not respond to reflex exposure. While slow charging has been found to make electrophotographic paper more sensitive, and thus produce better direct" copies, I have discovered that slow charging has an adverse effect upon the response of the paper to reflex exposure. In contrast, I have found that by limiting the charge formed on the copy paper, such as by increasing the speed at which the copy paper passes through the charging unit, the resultant copy paper exhibits unexpected reflexing characteristics.

This is to believed to be a result of the resulting limited, to wit, less than full charge, on the copy paper which produces a nonuniforrncharge distribution or potential gradient or the surface of the copy paper.

This effect has been demonstrated in a test in which a reflex copy was made while linearly increasing the speed of the copy through a single corona charging unit from approximately 0.5 inches per second to approximately 12 inches per second. The potential across the test charging unit was maintained at 6,000 volts. The paper so charged was then exposed to illumination having an intensity of 5,000 foot lamberts for a period of from 0.1 seconds at the top of the page to second at the bottom. The time exposure to the corona unit, or charging speed required, varies directly with the width of the charging unit aperture.

From this test it was determined that the particular paper used would not respond satisfactorily to reflex exposure at any level of illumination when charged at a speed of less than approximately 3 inches per second; but as the speed of charging was increased the exposure range over which the satisfactory copy was produced was broadened.

I believe the reason for this to be that in order for a paper to reflex the charge must be upon the immediate exposed surface of the photoconductive layer on the copy paper, as any appreciable preexposure of the paper will destroy its response to reflex exposure.

After the copy paper has been charged it is brought into face-to-face contact with the original documents. The copy paper and original are then exposed to a light source which is positioned behind the copy paper, so that light radiates through the copy paper and is reflected or absorbed at the face of the original document. The light reflected by the surface of the original discharges the charged photoconductive face of the copy paper lying adjacent thereto to produce a latent electrostatic image thereon.

Following the exposure the original document and copy paper are separated, and the paper is processed through a toner. In this manner a mirror image or laterally reversed copy of the original document is produced.

Duplicate copies of the original document are then made from the mirror image copy by direct exposure in the following manner. The mirror image copy is placed in face-to-face relationship with a charged sheet of electrophotographic paper and exposed to a light source which radiates through the mirror image copy and projects its image upon the photoconductive face of the copy paper. For this purpose the electrophotographic paper need not be especially dark adapted since it will be exposed to intensive light radiation. In this manner any number of duplicate copies of the original can be produced from the mirror image reflex copy.

The quality of the duplicate copies of the original may be improved by using electrophotographic paper coated on both sides. The double-coated paper is first exposed by the reflex method described above, and it is then processed by the direct exposure method which prints the mirror image through to its other side. This double-sided copy provides an excellent original for making duplicate copies by direct exposure, as the printing on both sides provides greater contrast for the direct process. Double-coated paper can also be used to produce paper having different printing on each side by direct face-toface exposure with two diflerent mirror image masters produced by reflex exposure.

Referring now to FIGS. 1-6, the parts of my machine will be described together with their function in the execution of the steps of my method.

Referring now to FIG. I, the device of my invention is comprised of a housing 1 within which the various feed rollers and other components to be described are supported in a manner familiar to those skilled in the art. Any conventional motor drive mechanism can be used to drive the moving parts of my invention, and conventional electrical circuits can be used to supply the electrical power required.

To make a reflex copy of a document 6 it is slipped face down into an input chute 3 in the top of housing 1, until it comes to rest upon a guide stop 7. Guide stop 7 is comprised of a shelf 6 (FIG. 2) which together with a wall 9 of chute 3 supports the lower edge of 6b of the original 6, or any document placed in chute 3 in preparation for coping. This frees the operator's hands and permits him to turn him complete attention to the insertion of a sheet of copy paper 10 into the machine. Guide stop 7,is further comprised of a ramp 1] which guides the leading edge 12 of copy sheet 10 up and against the original 6 to produce the feed effect to be discussed. It may be noted that while the original 6 is resting on guide stop 7 it shields incoming copy paper 10 from exposure by the sources of illumination within the machine.

With the original 6 so positioned, a sheet of dark-adapted electrophotographic copy paper 10 is then fed face up through an entrance 2 in the front of housing 1 into a first set of feed rollers 13 and 14. A shelf 15 positioned in front of feed rollers 13 and 14 supports copy paper 10' in position for pickup thereby.

Rollers 13 and 14 advance copy paper 10 through a corona charging unit 16 comprised of upper and lower pairs of fine wires 17 and 18, positioned across the path of the copy paper. The wires are shielded by grounded covers 19 and 20 which cage the corona and restrict its effect to linear apertures which face each other, and which are oriented across the path of the copy sheet and on opposite sides thereof.

The upper and lower parts of wires have opposite potentials impressed thereon of plus and minus 6,000 volts, the polarity depending upon the exposure procedure to be utilized, as will be explained.

While passing through charging unit 16 paper 10 is supported and guided by upper and lower insulated ribs 21 and 22 which are angled to the path of paper 10 to avoid masking it from charging wires 17 and 18.

Referring to FIG. 2, as paper 10 emerges from the charging unit 16, it is guided by ramp 11 up and against the face 60 of the original 6, dislodging its lower edge 611 from shelf 8 so that it falls against a rotating drum 25.

Rotating drum 25 has dual functions. It is the feed roller for the exposure element of my invention, and also a source of illumination. The core of drum 25 is a cylindrical lamp 26. This core is covered by a layer of soft, translucent, plastic sponge 27. Drum 25 rides parallel to end in sliding rolling contact with a stationary cylindrical lamp 29, which has a smooth surface. The pair is positioned opposite the exit of charging unit 16 with drum 25 in position to engage the lower edge 6b of the original when it falls from shelf 8 and carry it between drum 25 and light 29. Copy paper 10 shortly follows original 6 into the exposure element as it is urged through charging unit 16 by rollers 13 and 14.

Cylindrical lamp 29, and lamp 26 forming drum 25 comprise the exposure element of my invention. Only one of these lamps will be illuminated during a copy cycle, depending upon whether a reflex or direct copy is being made. It is necessary to have two sources of illumination, or one variable source of illumination, as l have found that reflex copying requires only from one tenth to one half the illumination normally used for making copies by direct exposure.

Reflex exposure takes place as previously described as the original 6 and the charged sheet of copy paper 10 pass between drum 25 and stationary lamp 29. Lamp 26 alone is illuminated; light from lamp 26 is reflected from the face 60 of the original and discharges the charged photoconductive surface of copy paper 10 in proportion to its intensity; so that variations in such reflection cause similar variations in the charge on the adjacent photoconductive face 10a of copy paper 10.

Referring to FIGS. 3, 4 and 5, as papers 6 and 10 emerge from the exposure unit, they enter a pair of separator and feed rollers 10 and 31, where the papers are separated. The first paper through will emerge a separator pawl 32 which is swivelly attached to the axle 33 of upper roller 30. Pawl 32 hooks over the leading edge of the first-emerging paper, and carries it up until pawl 32 is engaged by an ejector wheel 34. Wheel 34 is rotating at a speed which will flip pawl 32 clear of the emerging original 6. It is thus apparent that the original 6 must lead copy sheet 10 through the device by an amount sufficient to assure that only the original 6 will be picked up by pawl 20, or by about one eighth inch.

After the original 6 has engaged pawl 32, the exposed sheet of copy paper 10, fed by rollers 30 and 31, is diverted bya downwardly curved guide 35 to the developer tray 36. Tray 36 is concave and has ribs therein (not shown) parallel to he path of paper 10 to reduce friction between the tray and the paper.

Tray 36 contains a fluid toner of a type suitable for the copy paper used. The use of a fluid toner simplifies the developing process and machinery by eliminating the dust and handling problems associated with dry toners.

As the developed copy 10' emerges from tray 37, it is picked up and dried by a pair of pressure rollers 38 and 39 which also feed the developed copy 10' out of the machine into a receiving platform 40.

The reflex copy thus produced is a mirror image of the original. Duplicate copies of the original are made from this mirror image copy as follows. For the purpose of this discussion the mirror image copy will be referred to as the first copy.

The first copy is placed face down in chute 3 precisely in the manner of the original 6, coming to rest upon guide stop 7. A sheet of copy paper is then fed into the machine face up precisely as paper 10. These papers proceed through the machine face-to-face precisely as their counterparts 6 and 10 during the reflex copy cycle just described. However, in this case a direct exposure is made by illuminating lamp 29 instead of lamp 26. This change can be accomplished in any suitable manner.

Direct exposure is accomplished as the first copy and a charged copy sheet pass between roller and light 29. Light from lamp 29 passes through the top, or reflex, copy projecting the image thereon to the charged photoconductive surface of the copy paper below. The image produced on the copy paper is a mirror image of the first copy, and a duplicate of the original. Lamp 29 is a fluorescent tube having a strip of its inside coating about one-fourth inch wide removed along its line of contact with roller 25. A line high-intensity light is thus created, and restricted to the immediate area of exposure.

A light shield 28 is provided to protect an exposed copy sheet from random exposure after it leaves separation rollers and 31. Those skilled in the art will realize that other forms of light shielding may be employed throughout my machine if the sensitivity of the paper used requires it.

Direct copies of one-sided translucent, or nonopaque, originals may also be made by my device, as follows. The translucent original is placed into chute 3 in the manner of document 6, but face up. Copy paper 10 is fed through charging unit 16 face up as before. Copy paper 10 and the translucent original thus enter the exposure unit with the charged face 100 of the copy paper 10 against the back of the translucent original. Lamp 29 is used to print through the translucent original to the copy paper. The papers are then separated and the exposed copy paper developed as previously described.

The method and apparatus of my invention, as described, have the additional advantage of permitting the use of automatic feed for the copy paper. This is possible because the originals are fed into the device separate from the copy paper, whether to be copied by reflex or direct exposure.

An alternate method of making direct copies, which may be incorporated into my machine, is illustrated by FIG. 6 and 7. A translucent original 41 and a sheet of copy paper 42 are together fed into the machine of FIG. 1 through entrance opening 2, and a direct electrophotographic copy made in accordance with the teachings of my U.S. Pat. No. 3,288,605. The translucent original 41 is placed face down upon the back of a sheet of copy paper 42 forming a "set," with the leading edge 43 of the original 41 ahead of the leading edge 44 of the copy paper. The set" is fed through entrance opening 2 and into charging unit 16 by the first pair of feed rollers 13 and 14.

Means for reversing the polarity of the charging unit must be provided so that wires 17 and 18 will produce the appropriate charge on the downward-facing photoconductive surface of the copy paper 42.

The charged set is then exposed as it passes between illuminated lamp 29 and roller 25. From this point on the original 41 and exposed copy 42 are advanced through the machine exactly as their counterparts 6 and 10 during reflex copying.

Duplicate copies of opaque originals can also be made in this manner, using the first mirror image copy thereof, as an alternative process. In this instance item 41 FIG. 7 ans 8 will be the reflex copy (mirror image) of the original, placed face up upon the back of a face down sheet of copy paper 42.

A machine constructed and operated according to the foregoing specifications provides, for the first time, a lensless compact and inexpensive means of making electrophotographic prints of both translucent and opaque documents using a nontransfer process, In the nontransfer process, translucent originals and reversed reflex prints of opaque original can be processed in a single step; whereas in a transfer method the making of each copy direct or reflex is a two-step process. No transfer element, such as a drum, paper, or belt is required, and no complex optical system is necessary.

While the principles of the invention have been described in connection with the above specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of the invention as set forth in the accompanying claims.

What is claimed is:

1. A method for making a copy of an opaque original document comprising the steps of: making a mirror image electrophotographic copy of an original by reflex exposure, and making a laterally reversed electrophotographic copy of said mirror image copy by direct exposure producing a right-reading copy of the original, said copy-making step comprising the steps of electrostatically charging the photoconductive surface of a sheet of electrophotographic copy paper by passing said sheet through a charging unit at a rate between 3 inches per second and 12 inches per second to thereby establish a limited amount of electrostatic charge less than a full amount of charge on one surface of the copy paper, placing the photoconductive surface of the sheet of copy paper so charged against the face of the mirror image copy of the original document produced by the reflex exposure forming a set, exposing the set so formed to a predesignated amount of light from a light source positioned behind the reflex copy of the original document so that the light therefrom radiates through the reflex copy projecting its image upon the charged face of the copy paper, separating the set, and toning the sheet of copy paper so exposed to bring out the image thereon.

2. The method of claim 1 wherein the steps for making a laterally reversed copy of the mirror image copy produced by reflex exposure comprises the steps of:

placing the mirror image reflex copy back-to-back against a sheet of copy paper forming a second set, feeding the second set through a charging unit, charging the exposed photoconductive face of the sheet of copy paper as the second set passes through the charging unit,

exposing the second set to a predesignated amount of light radiating through the mirror image copy of the original document to the charged photoconductive surface of the copy paper.

3. A device for making copies of documents by a nontransfer electrophotographic process, comprising: electrostatic charging means of selected potential having an entrance and an exit, means for advancing a sheet of electrophotographic copy paper through said charging means at a selected rate of speed, so as to be exposed to said charging means for a selected relatively short period of time, to thereby establish a limited amount of charge on one surface of the copy paper, assembly means adjacent the exit of said charging means for bringing the charged face of the sheet of copy paper into contact with the printed face of the document to be copied forming a set, feed roller means including exposure means adjacent said assembly means for accepting the set from said assembly means and for exposing the set to light radiation of preselected intensity for illuminating the set through the back of the copy paper for preselected time interval and thereby effect reflex exposure of the copy paper, said exposure means comprising a ing edge of the copy paper and adjacent the exit of said charging means so that the leading edge of the charged copy paper will engage and push the leading end of the document causing it to enter said feed roller means ahead of the leading edge of roller including first cylindrical light source having an outer the copy papa covering of a translucent spongelike material and a stationary second cylindrical light source arranged substantially parallel to and contacting said roller, means for accepting the set from said exposure means and for separating the document to be copied from the exposed sheet of copy paper, and toning means for receiving the exposed sheet of copy paper from said separating means and for bringing out the latent electrostatic t image thereon.

4. The device of claim 3 wherein said assembly means further comprises means for supporting the leading end of the document to be copied across and below the path of the lead- 

2. The method of claim 1 wherein the steps for making a laterally reversed copy of the mirror image copy produced by reflex exposure comprises the steps of: placing the mirror image reflex copy back-to-back against a sheet of copy paper forming a second set, feeding the second set through a charging unit, charging the exposed photoconductive face of the sheet of copy paper as the second set passes through the charging unit, exposing the second set to a predesignated amount of light radiating through the mirror image copy of the original document to the charged photoconductive surface of the copy paper.
 3. A device for making copies of documents by a nontransfer electrophotographic process, comprising: electrostatic charging means of selected potential having an entrance and an exit, means for advancing a sheet of electrophotographic copy paper through said charging means at a selected rate of speed, so as to be exposed to said charging means for a selected relatively short period of time, to thereby establish a limited amount of charge on one surface of the copy paper, assembly means adjacent the exit of said charging means for bringing the charged face of the sheet of copy paper into contact with the printed face of the document to be copied forming a set, feed roller means including exposure means adjacent said assembly means for accepting the set from said assembly means and for exposing the set to light radiation of preselected intensity for illuminating the set through the back of the copy paper for preselected time interval and thereby effect reflex exposure of the copy paper, said exposure means comprising a roller including first cylindrical light source having an outer covering of a translucent spongelike material and a stationary second cylindrical light source arranged substantially parallel to and contacting said roller, means for accepting the set from said exposure means and for separating the document to be copied from the exposed sheet of copy paper, and toning means for receiving the exposed sheet of copy paper from said separating means and for bringing out the latent electrostatic image thereon.
 4. The device of claim 3 wherein said assembly means further comprises means for supporting the leading end of the document to be copied across and below the path of the leading edge of the copy paper and adjacent the exit of said charging means so that the leading edge of the charged copy paper will engage and push the leading end of the document causing it to enter said feed roller means ahead of the leading edge of the copy paper.
 5. The device of claim 4 wherein said means to support the leading edge of the document to be copied is comprised of a shelf having a supporting surface oriented generally parallel to the path of the copy paper and below the exit of said charging means, upon which the leading edge of the document to be copied rests until pushed off by the charged copy paper.
 6. The device of claim 3, in which said charging means comprises a corona charging unit having a limiting aperture. 